Lithium inks and electrodes and batteries made therefrom

ABSTRACT

Lithium metal powder based inks are provided. The inks are provided in formulations suitable for printing using a variety of printing techniques, including screen printing, offset litho printing, gravure printing, flexographic printing, pad printing and inkjet printing. The inks include lithium metal powder, a polymer binder and optionally electrically conductive materials and/or lithium salts in a solvent. The inks are well suited for use in printing electrodes for use in lithium metal batteries. Batteries made from lithium powder based anodes and electronic applications such as RFID labels, Smart Cards and wearable medical devices are also provided.

RELATED APPLICATIONS

This application claims priority to provisional patent application Ser.No. 60/545,179 filed Feb. 18, 2004 to Nelson and Wensley, which ishereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

The invention generally relates to lithium metal powder based inks,anodes made from the inks, and primary and secondary lithium metalbatteries made from the anodes.

BACKGROUND

Lithium primary and secondary batteries are an important component indeveloping many energy-related applications ranging from vehicles toconsumer electronics. The material properties of lithium, however,present problems in many applications, as well as in the manufacturingprocess. In particular, lithium foils can be difficult to work with andare not suitable for many important commercial applications particularlywhen ultra thin layers of lithium are desirable. A general need existsto improve the processability of lithium materials for use in batteriesfor a wide variety of applications. More particularly, better lithiummaterials are needed for use in polymer electrolyte batteries and thinfilm structures. Some efforts have been made to develop lithiumdeposition methods based on sprays or vapor deposition, but thesemethods can involve toxic solvents or expensive equipment. Alsoimportant is the ability to control the interface between theelectrolyte and the lithium electrode, particularly when the electrolyteis a solid and to control dendrite growth for secondary batteries.

Recently, attempts have been made to produce lithium battery anodes fromcompositions made from lithium powders. For example, PCT applicationpublication no. WO 02/21632 to Xeno Energy Co. describes a lithiumpowder anode. The anode is made from an emulsified lithium powder in aninorganic oil. However, this reference does not describe use of lithiumpowder in an ink form. Specifically, this publication does not describeuse of lithium powder in combination with a polymeric binders in asolvent. Furthermore, the compositions in this publication are limitedto those including lithium powders having relatively large averageparticle diameters.

U.S. Pat. No. 5,776,369 also describes preparation of lithium powdersusing an emulsion in hydrocarbon oil. The emulsified particles arefiltered from the oil. Particle size is 10 to 100 microns. Korean PatentApplication 1994-1781 also describes lithium powders. U.S. PatentPublication No. 2002/0119373 (U.S. Pat. No. 6,706,447) and 2004/0002005to Gao et al. describe lithium slurries for use in lithium batteryanodes. In the disclosed compositions, lithium metal powder and a hostmaterial are mixed with a non-aqueous liquid such as THF and a binder,and formed into a slurry. Alternatively, a lithium metal powder can beprovided in the anode by, for example, immersing the host material in asuspension containing lithium metal powder in a non-aqueous liquid suchas hydrocarbon solvent such as hexane. However, the compositionsdescribed in these publications are not formulated to be applied byprinting. Instead, the compositions are applied by casting. Anodesproduced using the compositions are quite thick, with average layerthicknesses of 50 to 150 microns.

In J. Power Sources, 93, 2001, 145-150), Kwon et al. also describelithium powder based anodes. The anodes are made from a powder slurrycontaining lithium powder (20-40 microns), PVdF binder, and THF. Likethe compositions of Gao et al, the compositions of Kwon are designed tobe cast into anodes and not printed.

SUMMARY

The invention is summarized in this non-limiting summary.

Lithium metal powder based inks, anodes made from the inks, and primaryand secondary lithium metal batteries made from the anodes are providedherein. The lithium powder based inks include a lithium metal powder, asolvent and a binder, and optionally an electronically conductivematerial and/or a lithium salt. In most battery applications, theelectronically conductive material is present. In particular, theinvention provides a lithium ink for use in printing an electrode for alithium battery, the ink comprising lithium metal powder, a hightemperature polymer binder and a solvent. In general, compositions areformulated to function as sophisticated ink formulations rather thanmere slurry compositions. For example, the ink spreading properties andviscosity can be carefully controlled, together with particle shape,particle size distribution, and average particle size.

The inks can be formulated to be printed onto substrates using a varietyof printing techniques, including screen printing, offset lithoprinting, gravure printing, flexographic printing, pad printing and inkjet printing. As such, the ink formulations provide significantadvantages over lithium powder compositions formulated for applicationby casting or spin coating. For example, printing techniques, such asoffset litho, gravure, flexographic, pad printing and ink jettechniques, allow for the high speed, high volume production of printedsubstrates (e.g. anodes) that is not possible with casting techniques.In addition, printing allows the inks to be applied in desired shapesand locations, which eliminates the need to punch out appropriatelyshaped sections from a larger film of cast ink, reducing waste. Printingalso makes it possible to form very thin layers of ink on a broad rangeof substrates, including flexible polymeric substrates and metalsubstrates. In some cases, layers of ink having an average thickness ofno more than about 30 microns, or even less, can be produced. Thisrepresents a substantial improvement over cast films of lithium powdercompositions which typically have an average film thickness of 50microns or greater.

The relative amounts of the various components that make up the inks mayvary depending a variety of factors, including the viscosityrequirements of the chosen printing method and conductivity requirementsof the intended application. The viscosity of the ink formulations maybe tailored to a chosen printing technique by changing the nature andamount of binder and/or solvent in the formulation, while theconductivity of the ink formulations may be tailored for a selectedapplication by changing the nature and amount of conductive materialsand the size of the conductive particles in the ink formulations. Insome embodiments, when the inks are printed onto a substrate, forexample using a screen printing process, they provide an ink layercontaining from about 20 to 50 percent lithium powder and from about 10to 30 percent polymer binder on a dry weight basis. This includesembodiments where the lithium powder based ink includes from about 30 to45 percent lithium powder, from about 15 to 20 percent polymer binder,from about 20 to 30 percent conductive material and from about 15 to 20percent lithium salt on a dry weight basis. However, the lithium powderbased ink formulations provided herein are not limited to those havingcomponents present in amounts falling within these ranges.

The lithium metal powder used to form the lithium inks can be a finelydivided lithium metal powder desirably having an average particle sizeof no greater than about 50 microns. In some instances, the lithiummetal powder has an average particle size of no more than about 1micron. Safety can be an issue in particle size and powder selection.Because the printing processes are capable of applying very thin layersof ink, in some cases the lithium powder size may be the limiting factorin minimizing the average layer thickness.

Binders can be included in the inks to adjust the viscosity of theformulations and to facilitate the adherence of the lithium metal powderparticles to a substrate, such as a metal anode current collector.Although a variety of polymer binders may be employed, it has beendiscovered that high temperature polymer binders, such as polyimidepolymer binders are well-suited for use with the inks provided herein.The polyimides may be pre-imidized polyimides and are desirably providedas amorphous, thermoplastic polyimide powders soluble in a polarsolvent, such as γ-butyrolactone. In some ink formulations, one or morepolyimides having a repeat unit weight per imide ring of no more than350 are employed.

The solvents used in the lithium powder based inks should be capable ofdissolving the polymer binder and should be sufficiently non-reactivewith the lithium powders for the application. In addition they should bevolatile enough to allow the inks to dry in a reasonable time frameafter printing, yet not so volatile that they evaporate prematurely,clogging printer parts, such as ink jet heads. In some instances thesolvent may be a solvent mixture. Not all solvents that are typicallyused in conducting ink formulations are well-suited for use as printingsolvents for lithium based inks. Generally, suitable solvents will beanhydrous aprotic organic solvents. The inventors have discovered, forexample, that gamma butyrolactone (GBL) is particularly well suited foruse in lithium powder based inks designed for printing applications,particularly when combined with a polyimide binder.

A conductive material may also be included in the ink formations toenhance their conductivity and to ensure good electrical contact betweenthe parts of electronics (e.g. batteries) into which they areincorporated. Typically these materials will take the form of aconductive powder. Examples of conductive materials that may be added tothe ink formulations include carbonaceous materials, such as carbonpowders and/or carbon nano-tubes. In some formulations, the amount ofconductive materials may be greater than the amount of lithium powder.

Lithium salts for use in the ink formulations include those lithiumsalts that are commonly used in lithium metal and lithium ion batteries.Many such salts are well known and commercially available. LiPF₆, LiBF₄,lithium perfluorosulfonate salts, and lithiumbis(trifluoromethanesulfonyl)imide (LiTFSi) are examples of a suitablelithium salts.

Anodes made from the lithium metal powder based inks include an anodecurrent collector and an electrode layer disposed on the anode currentcollector. Also provided from the invention is an anode comprising: (a)an anode current collector; and (b) an electrode layer disposed on theanode current collector, the electrode layer comprising lithium powderand a high temperature polymer binder. The electrode layer can be formedfrom the lithium powder based inks and includes lithium metal powder apolymeric binder and optionally, at least one conductive material and/orat least one lithium salt. The anode may be produced by printing alithium metal powder based ink onto a current collector, such as a metalfoil. However, more conventional application techniques, such as castingmay also be employed, although such techniques generally less efficientand more time consuming.

Primary and secondary batteries which incorporate the anodes providedherein include at least one anode, at least one cathode, and anelectrolyte in electrochemical communication with each anode and eachcathode. The batteries are characterized by high specific energydensities, high unit cell voltages, high specific capacities and longlifetimes and improved electrochemical stability. In some embodimentsmultiple parts, including anodes, cathodes and electrode layers may beproduced by printing. Also provided in this invention is a lithium metalbattery comprising: (a) a cathode; (b) an anode comprising a printedelectrode layer comprising lithium metal powder and a polymer binder;and (c) a polymer electrolyte sandwiched between the cathode and theanode.

The electrolyte may be a solid polymer electrolyte, a polymer matrixelectrolyte (PME), or a liquid electrolyte generally containing alithium salt. A battery based on a liquid electrolyte will typicallyinclude a separator film disposed between each anode and each cathodewith the liquid electrolyte distributed between each anode, each cathodeand each separator film. The liquid electrolyte desirably includes alithium salt, such as LiPF₆, in an organic solvent and the separatorfilms are typically porous organic polymer films saturated with theliquid electrolyte. Polymer electrolytes are generally gel typeelectrolytes which trap solvent and salt in the pores of the polymer toprovide a medium for ionic conduction.

Polymer Matrix Electrolytes provide an alternative to more conventionalliquid and solid polymer electrolytes. Polymer matrix electrolytesdiffer from solid polymer electrolytes in that once the polymer matrixelectrolyte is formed, the electrolyte is substantially free ofnon-absorbed solvent or identifiable pores. Instead, the solvent isintegrated with the polymer and the lithium salt in a homogeneous andsubstantially optically clear matrix. In addition, unlike conventionalgel polymers where the polymer only provides mechanical support, thepolymer, salt and solvent that make up the PME all participate in ionicconduction. In one exemplary battery construction, the electrolyte is aPME made from a polyimide, at least one lithium salt in a concentrationof at least, 0.5 moles of lithium per mole of imide ring provided bysaid polyimide and at least one solvent intermixed with the polyimideand the lithium salt to provide a polyimide matrix electrolyte which issubstantially optically clear.

Also provided are electronic devices, such as radiofrequencyidentification devices, Smart Cards, Time Temperature Indicators (TTI)and wearable external medical devices, powered by the batteries providedherein.

In another embodiment, provided is a lithium salt-based ink for use inprinting an anode for a lithium ion battery, the ink comprising anintercalation carbon material, a conductivity enhancing carbon material,a lithium salt, a high temperature polymer binder, and a solvent.

Various non-limiting, numbered, illustrative embodiments are describedas follows:

1. A lithium ink for use in printing an electrode for a lithium battery,the ink comprising lithium metal powder, a high temperature polymerbinder and a solvent.

2. The lithium ink of embodiment 1, wherein the high temperature polymeris capable of complexing with lithium salts and participating in ionicconduction.

3. The lithium ink of embodiment 2, wherein the high temperature polymerbinder comprises a polyimide.

4. The lithium ink of embodiment 2, wherein the high temperature polymerbinder comprises a polybenzimidazole.

5. The lithium ink of embodiment 2, wherein the high temperature polymerbinder comprises a polyamide-imide.

6. The lithium ink of embodiment 1, wherein the high temperature polymerbinder comprises a high temperature polymer selected from the groupconsisting of polyamides, polyphenylene oxides, polyarylates,polyester-imides, polyester-amide-imides, poly(benzoxazoles),polysulfones, polyether sulfones, polysulfonamides, poly(quinoxaline),poly(para-phenylenes), poly(aryl ethers) substituted with a pyridylgroup, poly(aryl ether sulfones), polyepoxides or a combination thereof.

7. The lithium ink of embodiment 1, wherein the high temperature polymerhas a glass transition temperature of at least 150° C.

8. The lithium ink of embodiment 2, wherein the high temperature polymerhas a glass transition temperature of at least 150° C.

9. The lithium ink of embodiment 3, wherein the polyimide comprises apre-imidized, amorphous, thermoplastic polyimide powder that is solublein a polar solvent.

10. The lithium ink of embodiment 1, further comprising at least oneelectronically conductive material.

11. The lithium ink of embodiment 1, further comprising at least onelithium salt.

12. The lithium ink of embodiment 1, wherein the lithium powder has anaverage particle size of no more than about 50 microns.

13. The lithium ink of embodiment 1, wherein the lithium powder has anaverage particle size of no more than about 20 microns.

14. The lithium ink of embodiment 1, wherein the lithium powder has anaverage particle size of no more than about 1 micron.

15. The lithium ink of embodiment 1, wherein the lithium powder has anaverage particle size of no more than about 100 nanometers.

16. The lithium ink of embodiment 1, wherein the ink has a viscosityfrom about 0.5 to 50 Pa-sec at 25° C.

17. The lithium ink of embodiment 1, wherein the ink has a viscosityfrom about 50 to 100 Pa-sec at 25° C.

18. The lithium ink of embodiment 1, wherein the ink has a viscosityfrom about 0.01 to 0.5 Pa-sec at 25° C.

19. The lithium ink of embodiment 3, comprising about 20 to 50 percentlithium powder, about 15 to 40 percent conductive material and about 10to 25 percent polyimide binder on a dry weight basis.

20. The lithium ink of embodiment 3, comprising about 50 to 70 percentlithium powder, about 30 to 40 percent conductive material and about 10to 15 percent polyimide binder on a dry weight basis.

21. The lithium ink of embodiment 1, wherein the solvent comprisesgamma-butyrolactone.

22. The lithium ink of embodiment 21, wherein the lithium powder has anaverage particle size of about 1 micron to about 100 microns, and theink further comprises at least one electrically conductive material andat least one lithium salt.

23. A lithium ink for use in printing an electrode for a lithiumbattery, the ink comprising a mixture of about 20 to 50 percent lithiumpowder and 10 to 50 percent polymer binder on a dry weight basis in apolar solvent.

24. The lithium ink of embodiment 23, wherein the polar solvent isgamma-butyrolactone.

25. The lithium ink of embodiment 23, further comprising an electricallyconductive material and a lithium salt.

26. The lithium ink of embodiment 23, wherein the lithium powder has anaverage particle size of no more than about 20 microns.

27. A lithium ink for use in printing an electrode for a lithiumbattery, the ink comprising lithium metal powder, a polymer binder, alithium salt and a solvent.

28. The lithium ink of embodiment 27 comprising from about 10 to 30percent lithium salt on a dry weight basis.

29. The lithium ink of embodiment 27 comprising from about 15 to 20percent lithium salt on a dry weight basis.

30. The lithium ink of embodiment 27 comprising about 30 to 45 percentlithium powder, about 20 to 35 percent conductive material, from about10 to 23 percent binder and from about 10 to 25 percent lithium salt ona dry weight basis.

31. The lithium ink of embodiment 27 having a viscosity of about 0.5 to100 Pa-sec at 25° C.

32. An anode comprising:

(a) an anode current collector; and

(b) an electrode layer disposed on the anode current collector, theelectrode layer comprising lithium powder and a high temperature polymerbinder.

33. The anode of embodiment 32, wherein the high temperature polymerbinder comprises a polyimide.

34. The anode of embodiment 32, wherein the lithium powder has anaverage particle size of no more than about 20 microns.

35. The anode of embodiment 32, wherein the lithium powder has anaverage particle size of no more than about 10 microns.

36. The anode of embodiment 32, wherein the lithium powder has anaverage particle size of no more than about 100 nanometers.

37. The anode of embodiment 33, wherein the polyimide polymer bindercomprises a pre-imidized polyimide.

38. The anode of embodiment 32 wherein the electrode layer has anaverage thickness of no more than 30 microns.

39. The anode of embodiment 32, wherein the electrode layer furthercomprises at least one electronically conductive material.

40. The anode of embodiment 32, wherein the electrode layer furthercomprises at least one lithium salt.

41. The anode of embodiment 33, wherein the polyimide comprises apre-imidized, amorphous, thermoplastic polyimide powder that is solublein a polar solvent, wherein the electrode layer further comprises atleast one electronically conductive material, and wherein the electrodelayer further comprises at least one lithium salt.

42. A battery comprising:

(a) at least one anode, the anode comprising:

-   -   (i) an anode current collector; and    -   (ii) an electrode layer disposed on the anode current collector,        the electrode layer comprising lithium metal powder and a high        temperature polymer binder; and

(b) at least one cathode; and

(c) an electrolyte in electrochemical communication with the eachcathode and each anode.

43. The battery of embodiment 42, wherein the high temperature polymerbinder comprises a polyimide.

44. The battery of embodiment 42, wherein the electrode layer has anaverage thickness of no more than 30 microns.

45. The battery of embodiment 42, wherein the electrolyte comprises asolid polymer electrolyte.

46. The battery of embodiment 42, wherein the electrolyte comprises apolyimide solid polymer electrolyte.

47. The battery of embodiment 46, wherein the electrolyte comprise about10 weight percent solvent or less.

48. The battery of embodiment 46, wherein the electrolyte comprisesabout 15 weight percent to about 40 weight percent solvent or less.

49. The battery of embodiment 42, wherein the lithium powder has anaverage particle size of no more than about 50 microns.

50. The battery of embodiment 42, wherein the lithium powder has anaverage particle size of no more than about 1,000 nm.

51. The battery of embodiment 49, wherein the binder comprises apre-imidized polyimide.

52. The battery of embodiment 42, wherein the electrolyte is opticallyclear.

53. The battery of embodiment 42, wherein the cathode comprises:

(a) a cathode current collector; and

(b) an electrode layer disposed on the cathode current collector, theelectrode layer comprising a polyimide, an electronic conductive fillerand a metal oxide.

54. The battery of embodiment 42, wherein the anode, cathode, andelectrolyte each comprise pre-imidized, amorphous, thermoplasticpolyimide that is soluble in a polar solvent.

55. The battery of embodiment 54, wherein the anode further comprises atleast one electronically conductive material and at least one lithiumsalt, and the electrolyte is optically clear and comprises at least onesolvent.

56. A lithium metal battery comprising:

(a) a cathode;

(b) an anode comprising a printed electrode layer comprising lithiummetal powder and a polymer binder; and

(c) a polymer electrolyte sandwiched between the cathode and the anode.

57. The battery of embodiment 56, wherein the electrode layer is printedon a current collector.

58. The battery of embodiment 57, wherein the electrode layer is printedon the polymer electrolyte.

59. The battery of embodiment 58, wherein the polymer electrolyte is apolyimide polymer matrix electrolyte.

60. The battery of embodiment 58, wherein the polymer binder is apolyimide binder.

61. The battery of embodiment 57, wherein the cathode is printed on acathode current collector.

62. The battery of embodiment 58, wherein the polymer electrolyte isprinted on the cathode.

63. The battery of embodiment 56, wherein the electrode layer isscreen-printed.

64. The battery of embodiment 56, wherein the electrode layer is offsetlitho printed.

65. The battery of embodiment 56, wherein the electrode layer is gravureprinted.

66. The battery of embodiment 56, wherein the electrode layer isflexographically printed.

67. A method of printing an anode for a lithium battery comprising:

-   -   formulating an ink according to embodiment 1,    -   printing the ink on a current collector.

68. The method according to embodiment 67, wherein the printing isscreen-printing.

69. The method according to embodiment 67, wherein the printing isoffset litho printing.

70. The method according to embodiment 67, wherein the printing isgravure printing.

71. The method according to embodiment 67, wherein the printing isflexographic printing.

72. The method according to embodiment 67, wherein the printing is inkjet printing.

73. The method according to embodiment 67, wherein the ink comprises apolyimide binder.

74. The method according to embodiment 67, wherein the ink furthercomprises at least one electronically conductive material.

75. The method according to embodiment 67, wherein the ink furthercomprises at least one lithium salt.

76. The method according to embodiment 67, wherein the lithium powder ofthe ink has an average particle size of about 10 nm to about 1,000 nm.

77. The method according to embodiment 67, wherein the lithium powder ofthe ink has an average particle size of about one micron to about 50microns.

78. A radiofrequency identification device powered by the battery ofembodiment 42 or embodiment 56.

79. The radiofrequency identification device of embodiment 78, whereinthe device is a Time Temperature Indicator.

80. A Smart Card powered by the battery of embodiment 42 or embodiment56.

81. A wearable medical device powered by the battery of embodiment 42 orembodiment 56.

82. The wearable medical device of embodiment 81, where the device isselected from the group consisting of external defibrillators, wearableinfusion pumps, patient monitors and electrical stimulation devices.

BRIEF SUMMARY OF THE DRAWINGS

FIG. 1 provides an example of a polyimide useful for the invention.

FIG. 2 provides an example of a polyimide useful for the invention.

FIG. 3 provides an example of a polyimide useful for the invention.

FIG. 4 illustrates an example of a fabrication scheme.

FIG. 5 illustrates an example of a patterned, printed layout.

FIG. 6 illustrates an example of a battery configuration.

DETAILED DESCRIPTION

I. Introduction

Provisional patent application Ser. No. 60/545,179 filed Feb. 18, 2004to Nelson and Wensley is hereby incorporated by reference in itsentirety including figures and claims.

Lithium metal powder based inks, anodes made from the inks, and primaryand secondary lithium metal batteries made from the anodes are providedherein. The inks are made from a solution or slurry of lithium metalpowder and a binder in an appropriate solvent. Optional ingredientsinclude conductive materials and lithium salts. The inks are well suitedfor fabricating anodes for low-profile, small volume lithium metalbatteries using simple printing techniques such as silk screen printingand high speed, high volume printing techniques, such as offset lithoprinting, gravure printing, flexographic printing, pad printing and inkjet printing.

Lithium batteries are generally described in, for example, LithiumBatteries, Science and Technology, (Eds. Gholam-Abbas Nazri andGianfranco Pistoria), Kluwer Academic, 2004, including both lithiummetal and lithium ion batteries. For example, section II describes anodematerials (including lithium alloys in chapter 9), and section IVdescribes electrolytes including polymer electrolytes (Chapter 19). Aseries of applications are described in Chapter 20 including batteryassembly, EV applications, HEV applications, stationary applications,and space applications. Medical applications are described in chapter21. Other examples of reference materials for lithium batteries include:(1) J. P. Gabano (Ed.), Lithium Batteries, Academic Press, London(1983); (2) H. V. Venkatasetty, (Ed.), Lithium Battery Technology, JohnWiley, New York (1984), and (3) G. Pistoia, (Ed), Lithium Batteries: NewMaterials, Developments, and Perspectives, Industrial Chemistry Library,Vol. 5, Elsevier, Amsterdam (1994).

II. Lithium Metal Powders

The lithium metal powders used in the production of the lithium inks canbe generally finely divided lithium metal powders, desirably having anaverage particle size of no more than about 500 microns, no more thanabout 100 microns or no more than about 50 microns. In some instancesthe average particle size of the lithium metal powder is not more thanabout 20 microns, in other instances the average particle size of thelithium metal powder is no more than about 10 microns and in still otherinstances the average particle size of the lithium metal powder is nomore than about 1 micron. For example, lithium metal powders having anaverage particle size from about 1 to 100 microns may be employed.Lithium powders can be lithium mixed with other compositions to formalloys and other mixtures.

The production of lithium metal powders suitable for use in lithium inkshas been described in the literature. For example, U.S. Pat. No.5,776,369, the complete disclosure of which is incorporated herein byreference, describes a method for preparing lithium metal powder havinga particle size of 10 to 100 microns. Another suitable lithium metalpowder and methods for its production are disclosed in PCT patentapplication no. PCT/KR00/01001, the entire disclosure of which isincorporated herein by reference. The lithium metal powders disclosed inthe above references are formed by dispersing molten lithium metal in aninert medium and cooling the dispersion to below the melting point ofthe lithium. Lithium metal powders suitable for use in the inkformulations provided herein are available commercially from Xeno EnergyCo. Ltd., (Seoul, KR).

Nanoscale lithium metal powders may also be used to formulate thelithium inks provided herein. As used herein a “nanoscale” lithium metalpowder is a lithium metal powder having an average particle size of nomore than about 1 micron. This includes powders having an averageparticle size of no more than about 500 nanometers, further includespowders having an average particle size of no more than about 100nanometers, still further includes powders having an average particlesize of no more than about 70 nanometers, yet further includes powdershaving an average particle size of no more than about 50 nanometers andstill further includes powders having an average particle size of nomore than about 20 nanometers. For example, the lithium metal powdersmay have an average particle size from about 10 to 1,000 nanometers. Thenanoparticles may be highly uniform in size and possess a high level ofpurity. The use of nanoscale particles is advantageous because suchsmall-scale particles may provide increased energy densities comparedwith larger diameter lithium powders. As such, the use of nanoscaleparticles makes it possible to produce batteries with higher capacitiesfor a given amount of lithium. The result is smaller batteries withlonger lifetimes.

III. Polymer Binders

The lithium inks may include at least one polymer binder. The binderforms a film in which the lithium powder is embedded once the ink hasdried. Blends of polymers can be used. Suitable polymer binders for usein some of the inks provided herein include, but are not limited to,polyvinylidene fluoride, polyethylene oxide, polyethylene,polypropylene, polytetrafluoroethylene, polyacrylates and mixtures andcopolymers thereof.

However, high temperature polymers having high glass transitiontemperatures are particularly desirable for use as binders in the inkformulations. High temperature polymers are a class of polymerswell-known to those skilled in the polymer field. These polymers aretypically used in the fabrication of articles which may be subjected tohigh temperatures (e.g. 400° C.-500° C., or greater). Special processingequipment may be needed to handle these high temperature polymers innormal processing because of the high glass transition. These materialsare characterized by high glass transition temperatures and, whencrystalline, melting points and are generally resistant to many solventsunless the polymer structure is modified to improve solubility.Polymers, including high temperature polymers, having functional groupscapable of complexing with lithium salts and participating in ionicconduction are particularly preferred. Suitable high temperaturepolymers include, polyimides, polyamides, polyphenylene oxides,polyarylates, polyamide-imides (PAI), polyester-imides,polyester-amide-imides, polybenzimidazoles (PBIs) andpoly(benzoxazoles). Polysulfones, polyether sulfones, polysulfonamides,poly(quinoxaline) (PPQ), poly(para-phenylenes), poly(aryl ethers)(PAE-2s) substituted with a pyridyl group, poly(aryl ether sulfones) andpolyepoxides may also be used. In some cases the high temperaturepolymers may be functionalized or modified to make them suitable for usein lithium metal batteries, as one of skill in the art would understand.Blends of polymers can be used including blends comprising the hightemperature polymer and also a different type of polymer to the extentthe application allows.

In some embodiments, the high temperature polymer is a polyimide that issubstantially soluble in the solvent used to formulate the lithium ink.Suitable polyimides for use in the inks provided herein are described inU.S. Pat. Nos. 5,888,672 and 6,451,480, the disclosures of which areincorporated herein by reference. The polyimides may be pre-imidized andare desirably provided as amorphous, thermoplastic polyimide powders.The use of amorphous polyimides is advantageous because, unlikecrystalline or semi-crystalline polymers, their amorphous natureprovides an unobstructed pathway for ionic mobility. Suitable polyimidesare commercially available. These include MATRIMID 5218 and 9725commercially available from Ciba-Geigy; ULTEM 1000 and 2000 commerciallyavailable from General Electric; and LaRC-CP1, LaRC-CP2 and LaRC-SI allof which are available from Imitec, Inc., Schenectady, N.Y. Othersuitable polyimides are described in U.S. Pat. Nos. 4,629,777 and4,474,858, the disclosures of which are incorporated herein byreference. Some ink formulations will include one or more polyimideshaving a repeat unit weight per imide ring of no more than about 350.Such polyimides are disclosed in pending U.S. patent applications Ser.Nos. 10/437,778; 10/437,559; and 10/437,546, filed May 13, 2003 toWensley et al., the disclosures of which are incorporated herein byreference. FIGS. 1-3 show the structures for three polyimides that maybe used as binders in the ink compositions provided herein.

In addition to polyimides, other generally glassy amorphous polymers canbe used including, for example, high glass transition temperaturepolymers (e.g., Tg greater than 150° C.; Tg greater than 180° C.; Tggreater than 200° C.; Tg greater than 250° C.; Tg greater than 350° C.).In general, the polymer can have polar groups which can complex withlithium salts and participate in ionic conduction. In some instances itis desirable to employ polymers having a Tg in the lower Tg rangebecause they are easier to process.

The solvents in the inks can be typically anhydrous, aprotic polarorganic solvents which are sufficiently chemically stable toward lithiummetal, and capable of solvating, the lithium powders, polymeric bindersand any conductive materials or lithium salts. Suitable polar solventsinclude, but are not limited to, gamma-butyrolactone (GBL),tetrahydrofuran (THF) and propylene carbonate (PC). GBL is particularlywell-suited for printing applications. Other suitable solvents includedioxane, 1,3-dioxolane, 1,2-dimethyloxyethane and dimethylsulfoxide.

IV. Other Components

Electronically conductive materials may also be added to the inks inorder to enhance their conductivity for a given application.Carbonaceous materials, such as carbon powder or carbon nano-tubes, maybe used to increase the conductivity of the inks. In addition, lithiumsalts may be added to the inks. LiPF₆, lithium perfluorosulfonate salts,and LiTFSi are well suited for use in the inks. Other suitable lithiumsalts include, but are not limited to LiCl, LiBr, LiI, LiBOB, LiClO₄,LiBF₄, LiAsF₆, and LiCF₃SO₃.

V. Alternative Embodiment

An alternative to the highly active lithium metal powder for inkformulation would be to substitute an intercalation carbon to absorblithium that came from another source. For example, the formulation cancontain (i) a fine carbon such as mesocarbon microbeads (MCMB) 6-10 or6-25 manufactured by Osaka Gas Chemical Co. LtD., (ii) a conductivityenhancing carbon such as Super P from TimCal Graphite & Carbon Co. orcarbon nanotubes, (iii) a binder polymer, (iv) a lithium salt, and (v) asolvent such as GBL or mixtures of solvents. This mixture would becapable of being printed and dried to provide a lithium active anode.The amounts of each of the components can be adjusted to provide aneffective ink formulation (e.g, viscosity, solids content) for aparticular application, substrate, and printing method. For example,binder polymers, lithium salts, and solvents described herein can beused including, in particular, high temperature polymers such aspolyimides and soluble polyimides. By way of background, MCMB electrodeformulations are described in, for example, U.S. Pat. Nos. 6,534,219;6,461,762; 6,174,627; 6,168,885; and 6,046,268.

VI. Printing and Formulations

Application techniques for the inks include both conventional coatingtechniques and printing techniques. For example, the inks can be coatedonto a surface, such as a current collector by vapor deposition, dipcoating, spin coating and brush coating. However, the inks arepreferably formulated to be printed onto a surface. Application of thelithium inks using printing methodologies is particularly advantageousbecause such methodologies allow for high speed, high volume applicationof the lithium inks to underlying substrates, such as metal currentcollectors. This is particularly advantageous in the manufacture oflithium metal batteries because it is simpler and faster than moreconventional production techniques where lithium metal foils arelaminated to anode current collectors. Moreover, printing the inkseliminates the need for more complicated and expensive coatingtechniques, such as vapor deposition. In addition, by printing the inksonto a surface, such as a current collector, better interfaces may beproduced and the need to spray a lithium composition is eliminated,reducing waste and environmental concerns. Many printing applicationalso make it possible to deposit very thin layers of the inks. Thisreduces cost and makes thinner electronic components possible. Forexample, depending upon the particle size of the lithium powder used toformulate the inks, layers of lithium ink having an average layerthickness of no more than about 40 microns may be printed. This includeslayers of ink having an average layer thickness of not more than about30 microns, further includes layers of ink having an average layerthickness of not more than about 20 microns and still further includeslayers of ink having an average layer thickness of not more than about10 microns.

The inks may be printed onto a substrate using a variety of printingmethods, including screen printing, offset litho printing, gravureprinting, flexographic printing, pad printing and ink-jet printing.

Screen printing uses a screen coated with a light sensitive emulsion orfilm, which blocks the holes in the screen. An image to be printed issupplied to the film. The imaged screen is then exposed to ultra-violetlight followed by the washing away of any light sensitive emulsion thathas not been hardened by the ultra-violet light. This leaves an openstencil which corresponds to the image that was supplied on the film.The screen is fitted on a press and the substrate to be printed isplaced in position under the screen while ink is placed on top of thescreen. A blade is pulled across the top of the screen, pushing the inkthrough the mesh onto the substrate to be printed. The lithium inkformulations for screen printing desirably have viscosities of about 0.5to 50 Pa-sec and more desirably 1 to 30 Pa-sec at 25° C. Using a screenprinting process, a layer of lithium powder based ink having an averagethickness of no more than about 30 microns and desirably no more thanabout 15 microns may be printed onto a substrate, provided the ink isprepared from a powder having a sufficiently small particle size.

In offset litho printing, generally, images are supplied to printingplates, which are dampened by ink which adheres to the image area. Theimage is then transferred to a rubber blanket, and from the rubberblanket to a substrate. Typical viscosities for lithium powder basedinks for use in offset litho printing are from about 10 to about 100 Pasat 20° C., desirably from about 30 to 80 Pas at 20° C. Offset lithoprinting is capable of providing very thin layers of ink. In fact thelayer thickness of the printed ink may be limited by the particle sizeof the lithium powder. For example, if lithium powder having smallenough particle sizes are employed, lithium powder based inks can beapplied in layers having an average thickness of from about 0.5 to 2microns.

Gravure printing uses, generally, a cylinder onto which an image hasbeen engraved with cells. To print, the cells are filled with ink andthe substrate to be printed is passed between the printing cylinder andan impression roller. The lithium powder based inks used with gravureprinting typically have viscosities much lower than those used withscreen or offset litho printing. For example, some gravure printing inkswill have a viscosity from about 0.01 to 0.5 Pa-sec at 25° C., desirablyfrom about 0.05 to 0.2 Pa-sec at 25° C. Like offset litho printing,gravure printing is capable of printing very thin layers of lithium ink.For example, depending on the size of the lithium powders used, gravureprinting may be used to print lithium ink in layers having an averagethickness of about 0.8 to 8 microns.

In flexographic printing, a screened roller is generally used to apply athin layer of relatively fluid ink to the surface of a flexible printingplate. A rotating plate roller is then used to bring the inked surfaceof the printing plate into contact with a web to be printed and animpression roller presses the web against the plate to effect thetransfer of the ink. The lithium ink formulations for flexographicprinting have viscosities similar to those used for gravure printing,desirably from about 0.01 to 0.7 Pa-sec and more desirably 0.05 to 0.5Pa-sec at 25° C. Depending on the size of the lithium powders used toformulate the inks, flexographic printing may be used to produce inklayers with an average thickness from about 0.5 to 5 microns, desirablyfrom about 0.8 to 2.5 microns.

In pad printing an image to be transferred generally is etched into aprinting plate known as a cliché. The cliché is initially flooded withink and then cleaned to leave ink only in the image area. A silicontransfer pad is then positioned over the cliché and pressed onto it totransfer the ink. The pad is lifted away from the cliché and the ink isallowed to partially dry, rendering it tackier and more viscous. The padis then pressed onto a substrate where the ink is deposited. Lithiummetal powder based ink formulations for pad printing will haveviscosities similar to those of the screen printing ink formulations.

Ink jet printers generally use a series of nozzles to spray drops of inkdirectly on the paper. Ink jet printers are typically used with inkshaving viscosities of about 0.001 to 0.05 Pa-sec at 25° C. and canproduce ink layers having an average thickness of about 0.1 to 30microns, desirably 0.3 to 20 microns.

The lithium powder based inks can be provided in a number of differentformulations to be used with different printing processes for differentapplications. Two of the primary considerations when choosing aformulation are the viscosity and conductivity of the ink. As notedabove, the viscosity requirements of an ink may vary dramatically basedon the printing technique to be used. Viscosity will depend, at least inpart, on the amount of solvent and polymer binder present in thecomposition, and, in particular, on the ratio of the total amount oflithium powder and conductive material to binder in the composition.Another consideration, that can be taken together with viscosityconsiderations, is the conductivity requirements for a givenapplication.

Several exemplary embodiments of lithium powder based ink compositionsare provided below.

In some embodiments, the ratio of (lithium powder+any conductivematerial+any lithium salt): polymer binder in the lithium powder basedinks may be between 3:1 and 6:1. These embodiments are well-suited foruse in screen printing applications. In certain embodiments the inkcontains from about 20 to 50 percent lithium powder, from about 15 to 40percent conductive material and from about 10 to 25 percent polymerbinder on a dry weight basis, where the dry weight would include thelithium powder and any optional conductive material or lithium salt.This includes embodiments wherein the ink contains from about 30 to 45percent lithium powder, from about 20 to 35 percent conductive material,from about 15 to 23 percent binder, and optionally from about 10 to 25percent lithium salt on a dry weight basis. Typically ink formulationsfitting these descriptions will be dissolved in an appropriate solventat about 10 to 25 percent. In some formulations of this type, the binderis a polyimide binder, the conductive material is carbon powder, thelithium salt is LiPF₆ or LiTFSi and the solvent is GBL.

Higher viscosity lithium powder based inks may also be produced.Depending on their viscosities, such inks may find use as offset lithoprinting inks. Such inks are typically significantly less dilute thatscreen printing inks. In some embodiments these inks contain from about40 to 80 percent lithium powder, from about 30 to 70 percent conductivematerial and from about 10 to 20 percent polymer binder on a dry weightbasis, where the dry weight would include the lithium powder and anyoptional conductive material or lithium salt. This includes embodimentswherein the ink contains from about 50 to 70 percent lithium powder,from about 30 to 40 percent conductive material, from about 10 to 15percent binder, and optionally from about 5 to 15 percent lithium salton a dry weight basis. Typically ink formulations fitting thesedescriptions will be dissolved in an appropriate solvent at about 30 to80 percent, desirably about 40 to 60 percent. In some formulations ofthis type, the binder is a polyimide binder, the conductive material iscarbon powder, the lithium salt is LiPF₆ or LiTFSi and the solvent isGBL.

Lithium powder based inks that may find use as flexographic or gravuremay have a ratio of (lithium powder+any conductive material+any lithiumsalt):polymer binder of between 3:1 and 8:1. In some such embodimentsthe ink contains from about 30 to 60 percent lithium powder, from about20 to 50 percent conductive material and from about 2 to 15 percentpolymer binder on a dry weight basis, where the dry weight would includethe lithium powder and any optional conductive material or lithium salt.This includes embodiments wherein the ink contains from about 40 to 50percent lithium powder, from about 20 to 30 percent conductive material,from about 5 to 10 percent binder, and optionally from about 10 to 20percent lithium salt on a dry weight basis. Typically ink formulationsfitting these descriptions will be dissolved in an appropriate solventat about 5 to 20 percent, desirably about 10 to 15 percent. In someformulations of this type, the binder is a polyimide binder, theconductive material is carbon powder, the lithium salt is LiPF₆ orLiTFSi and the solvent is GBL.

One application for which the lithium powder based inks provided hereinare useful is in the production of electrodes, such as anodes forlithium metal batteries. Such anodes may be fabricated with the lithiummetal powder based inks provided herein by printing the ink onto thesurface of an anode current collector. The anode current collector is anelectrically conductive member made from a metal, such as aluminum,copper, nickel, iron or stainless steel. The current collector may be afoil or a grid.

VII. Batteries

The anodes provided herein may be incorporated into both primary andsecondary lithium metal batteries. Although different batteryconstructions are possible, each battery will include at least oneanode, at least one cathode and an electrolyte in electrochemicalcommunication with each anode and each cathode. Such batteries representan improvement over more conventional lithium metal based batteriesbecause the lithium metal powder based anodes tend to suppress theformation of dendrites, extending the lifetime of the batteries.

Lithium metal batteries and related materials into which the anodesprovided herein may be incorporated are described in, for example, U.S.Pat. Nos. 5,888,672 and 6,451,480 to Gustafson, as well as pending U.S.patent application Ser. Nos. 10/437,778; 10/437,559; and 10/437,546, allfiled May 13, 2003 to Wensley et al., which are hereby incorporated byreference in their entirety and can be used for the practice of thepresent invention.

One or more anodes in the battery are composed of a current collectorwith an electrode layer of lithium metal powder in a polymer binder,disposed thereon. The anodes may be formed by printing a lithium powderbased ink, of the type described above, onto the current collector andallowing the ink to substantially dry.

The electrolyte may be any suitable electrolyte for use in a lithiummetal battery, many of which are known and commercially available.Suitable electrolytes include liquid electrolytes, solid polymerelectrolytes and polymer matrix electrolytes (PMEs). In order to provideionic conductivity to the anode, the electrolytes include at least onelithium salt. Lithium salts that may be used in the electrolytesinclude, but are not limited to, LiCl, LiBr, LiI, LiClO₄, LiBF₄, LiAsF₆,Li(CH₃CO₂), Li(CF₃SO₃), Li(CF₃SO₂)₂N, Li(CF₃SO₂)₃C, Li(CF₃CO₂),Li(B(C₆H₅)₄), Li(SCN), and Li(NO₃). LiPF₆ and LiTFSi are particularlywell-suited for use in the electrolytes.

Batteries that use a liquid electrolyte include a separator filmdisposed between each anode and each cathode. In this construction, theseparator films are typically porous organic polymer films saturatedwith the lithium salt electrolyte solution. Any separator film known tothose skilled in the art may be used as a barrier between each anode andcathode layer. The separator film is typically a freestanding filmcomprised of an organic polymer, such as polypropylene, polyethylene orpolyvinylidene fluoride, and is generally saturated with a liquidlithium electrolyte solution. Examples of such films include but are notlimited to Kynar-FLEX from Atochem North America; and CELGARD 3401 fromCelgard, Inc.

Solid polymer electrolytes can be generally gel type electrolytes, whichtrap solvent and salt in the pores of the polymer to provide a mediumfor ionic conduction. The polymer electrolytes generally can function asseparators between anodes and cathodes and as electrolytes. Polymerelectrolytes may be made from such polymers as polyethylene oxide (PEO),polyether based polymers and other polymers, which are configured asgels, including polyacrylonitrile (PAN), polymethylmethacrylate (PMMA)and polyvinylidine fluoride (PVDF).

In some embodiments of the batteries provided herein, the electrolyte isa polymer matrix electrolyte. In these PMEs, a solvent is integratedwith the polymer and a lithium salt in a homogeneous and substantiallyoptically clear matrix. As a result the PMEs are substantially free ofnon-absorbed solvent or identifiable pores. Unlike conventional gelpolymers where the polymer only provides mechanical support, thepolymer, salt and solvent that make up the PME all participate in ionicconduction. Suitable PMEs for use in the batteries provided herein aredescribed in pending U.S. patent application Ser. Nos. 10/437,778;10/437,559; and 10/437,546, all filed May 13, 2003 to Wensley et al. Inone exemplary embodiment, the PME includes a polyimide, at least onelithium salt in a concentration of at least 0.5 moles of lithium permole of imide ring provided by the polyimide and at least one solvent,all intermixed. The PME is generally homogeneous as evidenced by itshigh level of optical clarity. As used herein, when the PME is referredto as being substantially optically clear. The phrase “substantiallyoptically clear” regarding the PME refers to the PME being at least 90%clear (transmissive), preferably at least 95%, and most preferably beingat least 99% clear as measured by a standard turbidity measurement,transmitting through a normalized 1 mil film using 540 nm light.

The lithium salt is desirably present in an amount between 0.5 and 2.0moles Li per mole of imide ring provided by the polyimide, or 1.2 and2.0 moles Li per mole of imide ring provided by the polyimide. Preferredlithium salts for use with PMEs include LiCl, LiBr, LiI, LiBOB, LiClO₄,LiBF₄, LiAsF₆, LiPF₆, LiTFSi, LiCF₃SO₃, and LiN(CF₃SO₃)₂.

A repeat unit weight per imide ring of the polyimide may be no more than350, no more than 300, or no more than 250. The polyimide is preferablysoluble at 25° C. in at least one solvent selected from the groupconsisting of N-methylpyrrolidinone (NMP), dimethylacetamide (DMAc) anddimethylformamide (DMF).

The ionic conductivity of the PME at 25° C. is desirably at least 1×10⁻⁴S/cm, and preferably at least 3×10⁻⁴ S/cm. The PME desirably provides atleast one infrared absorption between about 1630 and 1690 cm⁻¹, eventhough neither the salt nor the polyimide provide any absorption peaksin this range. Solvent can be included in the PME to improveconductivity and other properties. For example, solvent content of thePME can be about 15 wt. % to about 40 wt. % for applications whereinhigh discharge rates or lower temperatures are needed. Solvent contentof about 10 wt. % or less can be used for other applications. Forpolyimide systems, it can be difficult to remove all solvent.

The cathodes used to construct the batteries may be any cathode materialsuitable for use with lithium metal batteries, many of which are known.For example, the cathode may comprise a polymer binder, an intercalationmaterial, and an electrochemically active material. Theelectrochemically active material is desirably a metal oxide, such asMnO₂ or a lithium metal oxide, such as a lithium vanadium oxide(Li_(x)V_(y)O_(z)), a lithium transition metal oxide (e.g. LiMn₂O₄),LiCoO₂, LiNiO₂, Li₄Ti₅O₁₂, LiV_(x)O_(y), a metal sulfide (e.g. TiS₂) andLiFePO₄. The polymer binder may be a polyimide, including thosedescribed in U.S. Pat. Nos. 5,888,672 and 6,451,480, or even aconductive polyimide, such as those described in pending U.S. patentapplication Ser. Nos. 10/437,778; 10/437,559; and 10/437,546, all filedMay 13, 2003 to Wensley et al. When the anode and the electrolyte and/orthe cathode each include a polyimide, they may all include the same ordifferent polyimides. Suitable intercalation materials include, but arenot limited to, carbon black and graphite.

In one embodiment, the cathode comprises a cathode current collectorhaving an electrode layer disposed thereon, wherein the electrode layerincludes an amorphous, thermoplastic polyimide, an electronic conductivefiller and a metal oxide. Cathodes of this type are described in U.S.Pat. No. 5,888,672.

One procedure for producing the cathode is as follows: a slurry of anelectrochemically active material, a polymer binder and an intercalationmaterial in a solvent is formed. The slurry is then coated or printedonto a cathode current collector, such as a aluminum or nickel foil, andthe solvent is allowed to evaporate.

VIII. Battery Fabrication

Fabrication of batteries using the lithium powder based electrodes canbe carried out with known methods as well with methods as describedherein. One or more batteries can be fabricated quickly and efficientlyusing printing technologies wherein a lithium metal powder based anode,a polymer electrolyte and a cathode are all printed using screenprinting or other printing techniques.

The lithium powder based inks provided herein make it possible tofabricate a battery in which all three components are printed. Forexample, a printed lithium battery may be produced by printing a slurryof an electrochemically active material, such as a lithium metal oxide,a polymer binder, such as a polyimide and an intercalation material,such as graphite in an appropriate solvent onto a metal foil or meshcurrent collector and allowed to dry to provide a cathode. A polymerelectrolyte may then be printed over the printed cathode by printing asolution of a polymer binder, such as a polyimide, a lithium salt and anappropriate solvent onto the cathode. The electrolyte is allowed to dryto remove solvent with an effective amount of solvent retained forconductivity purposes, such as, for example, 5 to 50 weight % versuspolyimide plus salt. At this point the overcoated cathode has becomeboth the cathode and the membrane separator. The anode may be eitherprinted directly onto the printed polymer electrolyte or onto a metalcurrent collector, which is then placed over the printed polymerelectrolyte. PMEs are well-suited for use in printed lithium batteriesbecause, unlike conventional polymer electrolytes, they do not includefree solvents or gel which might interfere with the printing process orthe quality of the final printed layers.

Of course, it is not necessary that the anode, cathode and electrolytebe printed. One or more these components may be cast or otherwiseprocessed. In one exemplary fabrication process a separator is cast froma solution as a free-standing film. The separator is then sandwichedbetween a cathode, which may be printed or cast onto a currentcollector, and an anode, which may be printed or cast onto a currentcollector. The layers are then laminated together under heat andpressure. If the cell is based on a polymer electrolyte, the separatoralso serves as the electrolyte. If the cell is based on a liquidelectrolyte, the liquid electrolyte is introduced into the system toprovide electrochemical communication between the anode and cathode.

The battery can be a packaged battery, wherein the metal currentcollectors form a packaging material surrounding the battery. In thisembodiment, the current collectors serve as moisture barriers, currentcollectors and exterior electrical connection means. FIG. 4 shows how aprinted packaged lithium powder based battery can be fabricated. Asshown in the figure, a roll of metal foil 400, such as a copper foil,may be cut into individual anode current collector sheets 402 which arepassed into a silk screen press 404. In the press, a lithium powderbased ink is screen printed onto one side of the metal foil sheet toform an array of anodes 406. FIG. 5 shows an enlarged view of theprinted sheet 406, having an array of anodes 502 printed thereon. Asshown in the figure, each anode is surrounded by a perimeter area ofcurrent collector 504 where there is no printed anode material. Theprinted sheet is then passed into a drying tunnel 408, which may be anoven, to promote drying of the ink. Fast drying facilitates fastproduction and is desired generally. The sheet is then fed into acalendaring press 410.

The cathode and electrolyte can be formed by a similar process. First aroll of metal foil 412, such as an aluminum foil, is cut into individualcathode current collector sheets 414 which are passed into a silk screenpress 416. In the press, a slurry of a polymer binder, an intercalationmaterial and an electrochemically active material is screen printed ontoone side of the metal foil sheet to form an array of cathodes 418. Theprinted cathode sheet is then passed into a drying tunnel 420 and theninto a calendaring press 422. The cathode sheet is then fed into anothersilk screen press 424 where an array of electrolytes 426 is printeddirectly over the array of cathodes 418. In the case where theelectrolyte is a PME, a slurry of an appropriate polyimide binder, alithium salt and a solvent may be used as the printing ink. The printedsheet is then passed through another drying tunnel 428. Upon exiting thedrying tunnel, the printed sheet may be passed through a spray station430 where it is sprayed with a small amount of solvent to promoteadhesion to a sealant frame layer 432. The sealant frame serves to bondthe anode layer and the cathode/electrolyte layers around the perimeterof each cell. The frame is formed from a roll of polymeric film 434,such as a polyester film, having a heat sealable adhesive applied bothsides. The film 434 is cut into individual sheets and an array of“windows” 436 is cut into each sheet. This may be accomplished, forexample, using a laser cutter 438 or a window punch. The polymeric sheetis then sandwiched between the printed side of the anode sheet 446 andthe printed side of the cathode/electrolyte sheet 448 with its array ofwindows lined up with the anode, cathode and electrolyte arrays. Thisstacked structure 440 is then laminated in a lamination press 442. Inthe resulting structure, the polymeric sheet seals to both currentcollector foils in a perimeter area around the individual cells wherethere is no printed electrode or electrolyte materials. The stacked,laminated structure may then be subjected to a punching process tosingulate the individual battery cells. The cells may then be sent on toa testing station and, finally, to a packaging station, such as a tapeand reel packaging station 444.

FIG. 6 shows a battery which, if desired, can be made in accordance withthe process outlined in FIG. 4. The battery includes a copper anodecurrent collector 600, a printed lithium metal powder based anode 602, aprinted PME 604, a printed cathode 606 and an aluminum cathode currentcollector 608. The anode and cathode current collectors 600, 608 aresealed around the perimeter of the battery with a polyester sealantframe 610.

IX. Battery Applications

The lithium metal batteries provided herein may be used to powerelectronic devices that use ultrathin, flexible batteries. Althoughthese devices have proven useful in a broad range of applications, theirpenetration into some markets has been stalled by size and costconsiderations. Frequently, it is the size and cost of production of thebattery that powers these devices that prove to be the limiting factors.As discussed above, the lithium powder based inks provided herein, allowfor the high speed, high volume production of printed lithium powderanodes and lithium metal batteries. The batteries so produced have thepotential to be thinner and less costly to produce than lithium metalbatteries made by more conventional techniques.

Examples of applications that may be powered by the present batteriesinclude, but are not limited to, sensors, medical applications, militaryapplications, security applications, music, audio and broadcastapplications, computing applications, financial transactionapplications, transportation applications and measuring and meteringapplications. Specific examples of sensors include tracking andidentification sensors (e.g., Smart Cards, radiofrequency identification(RFID) tags, biometric sensors and friend or foe identificationdetectors). These sensors are useful in homeland security applicationswhere they may be used to track and/or identify baggage and passengersand to authenticate documents such as passports and visas. Other sensordevices include emergency, security and environment sensors (e.g., firealarms, smoke detectors, motion detectors, chemical sensors, temperaturesensors, time-temperature indicators, humidity sensors and acousticseismic sensors). These sensors may take the form ofmicroelectromechanical sensors (i.e., “Smart Dust” sensors). Specificexamples of medical devices include external wearable medical devices(e.g., ambulatory infusion pumps), telemetry systems, blood analyzers,bone growth stimulators, Holter monitors, pulse oximeters, externalpacemakers and defibrillators. Specific examples of military devicesinclude communications devices (e.g., wireless transmitters), thermalimaging devices, night vision devices, surveillance devices, underseamines, military radios, guidance and positioning system, search andrescue transponders, radar jammers, respiratory protection suits andsonobuoys. Music, audio and broadcast devices include wirelessmicrophones, transmitters and amplifiers. Specific examples of computingdevices include computer clocks and memory backup devices. Specificexamples of financial transaction applications include both securetransaction devices (e.g., Smart credit and debit cards) and non-securetransaction devices (e.g., gift and loyalty cards). It should beunderstood that this list of possible applications is not intended to beexhaustive.

An RFID label includes identification data carried on a silicon chip. Anantenna is provided to transmit a radiofrequency signal that can bedetected at a distance. Using this antenna the chip receives andtransmits data. A “smart” RFID label is one which can track, process andstore data. The lithium metal batteries provided herein may be used topower the radiofrequency transmitter of the smart active labels toincrease their data transmission rate and data transmission range.

Time Temperature Indicators (TTIs) are a type of RFID label that may bepowered by the lithium metal batteries provided herein. TTIs are labels,typically self adhesive labels, that are affixed to or incorporated intofood packaging to monitor the temperature history of the food on its wayto the customer. These labels are used to help identify spoiled foodsand remove them from the chain of distribution. The RFID TTIs may beused to track and store the full temperature history of the food and toprovide a signal to indicate the “freshness condition” of the food basedon its temperature history.

Smart Cards are cards, typically about the size of a credit card, thatcontain electronics, such as integrated circuits, for retrieving,processing, transmitting and storing information. A Smart Card includesat least one plastic layer, a battery and at least one electronic device(i.e. electronic circuit) embedded in the plastic layer. The lithiummetal batteries provided herein may be used to power the electronicdevice of a Smart Card to allow for the storage of greater amounts ofdata and improved processing capabilities.

The thin, flexible and light-weight nature of the lithium metalbatteries provided herein also makes them well suited for poweringwearable medical devices, including external defibrillators, wearableinfusion pumps, patient monitors and electrical stimulation devices.

EXAMPLES

The present invention is further illustrated by the followingnon-limiting examples. These examples are provided for illustration onlyand are not to be construed as limiting the scope or content of theinvention in any way.

Example 1 Lithium Metal Powder Ink

A quantity of 26.5 grams of the polyimide shown in FIG. 1 is dissolvedin enough GBL to produce a solution containing 20 weight percent of thepolyimide. A more general description of the polyimide is provided inU.S. Pat. No. 4,629,777. A quantity of 17.8 grams of LiTFSi salt isdissolved in enough GBL to produce a solution containing 20 weightpercent of the salt. Equal masses of the two resulting solutions arethen mixed and 178 grams of the mixture is added to a suspension of 37.9grams of lithium powder and 26.5 grams of carbon powder in 574 grams ofGBL. The final mixture is shaken well to ensure complete particlewetting by the solvent thus creating a uniform slurry.

The experiment can be repeated with the polymers shown in FIGS. 2 and 3as desired.

Example 2 Lithium Metal Powder Based Anode

A lithium metal powder based anode is produced in a dry atmosphere asfollows. A 3″×5″ piece of copper foil is mounted below the silk-screenpress of a silk-screen printer. The silk-screen press is then loweredonto the copper foil and the slurry of Example 1 is applied over thescreen. A flat edge is dragged over the screen to transfer the slurrythrough the screen and onto the copper foil. The press is opened and theprinted foil is removed. It takes about 30 seconds to mount the foil,lower the press, apply the slurry, open the press and remove the film.This equates to about 12 anodes printed per minute. If desired, theprinted anodes may be transferred to a convection oven on a conveyor fordrying. The coating is desirably allowed to dry until it has asolid-like appearance, although a residual GBL content of about 15 to 20weight percent remains. The printed anodes are suitable for use asanodes in lithium metal batteries.

All references described herein are incorporated by reference in theirentirety.

While the preferred embodiments of the invention have been illustratedand described, it will be clear that the invention is not so limited.Numerous modifications, changes, variations, substitutions andequivalents will occur to those skilled in the art without departingfrom the spirit and scope of the present invention as described in thefollowing claims.

1. A lithium ink for use in printing an electrode for a lithium battery,the ink comprising; 20 to 80 percent lithium metal powder; 10 to 25percent of a polymer binder; optionally, an electrically conductivematerial other than lithium metal powder; a lithium salt; and a solvent;wherein the percentages are calculated on a dry weight basis; andwherein the lithium metal powder is formed by dispersing molten lithiummetal in an inert medium and cooling the dispersion to below the meltingpoint of the lithium.
 2. The lithium ink of claim 1, wherein the polymeris capable of complexing with lithium salts and participating in ionicconduction.
 3. The lithium ink of claim 2, wherein the polymer bindercomprises a polyimide, a polybenzimidazole or a polyamide-imide.
 4. Thelithium ink of claim 1, wherein the polymer binder comprises a polymerselected from the group consisting of polyamides, polyphenylene oxides,polyarylates, polyester-imides, polyester-amide-imides,poly(benzoxazoles), polysulfones, polyether sulfones, polysulfonamides,poly(quinoxaline), poly(para-phenylenes), poly(aryl ethers) substitutedwith a pyridyl group, poly(aryl ether sulfones), polyepoxides andcombinations thereof.
 5. The lithium ink of claim 1, wherein the polymerhas a glass transition temperature of at least 150° C.
 6. The lithiumink of claim 3, wherein the polyimide comprises a pre-imidized,amorphous, thermoplastic polyimide powder that is soluble in a polarsolvent.
 7. The lithium ink of claim 1, wherein the lithium metal powderhas an average particle size of no more than about 50 microns.
 8. Thelithium ink of claim 1, wherein the lithium metal powder has an averageparticle size of no more than about 1 micron.
 9. The lithium ink ofclaim 3, wherein the polymer binder comprises a polyimide.
 10. Thelithium ink of claim 1, wherein the solvent comprisesgamma-butyrolactone.
 11. A method comprising: printing the lithium inkof claim 1 onto a substrate; and allowing the ink to dry to form aprinted layer on the substrate.
 12. The method of claim 11, whereinprinting is selected from the group consisting of: screen printing,offset litho printing; gravure printing; flexographic printing; padprinting and ink jet printing.
 13. The method of claim 11, wherein theprinted layer has an average thickness of 40 microns or less.
 14. Themethod of claim 12, wherein printing comprises screen printing.
 15. Themethod of claim 14, wherein the printed layer has an average thicknessof no more than 30 microns.
 16. The method of claim 12, wherein printingcomprises flexographic printing.
 17. The method of claim 16, wherein theprinted layer has an average thickness of 0.5 to 5 microns.
 18. Themethod of claim 12, wherein printing comprises ink jet printing.
 19. Themethod of claim 18, wherein the printed layer has an average thicknessof 0.1 to 30 microns.
 20. A method of making a battery comprising firstand second metal current collectors, an anode, a cathode and a polymerelectrolyte layer comprising: printing the lithium ink of claim 1 ontothe first metal current collector; allowing the ink to dry to form thecathode; printing a composition comprising a polymer binder, a lithiumsalt and a solvent on the cathode; allowing the composition to dry toform the polymer electrolyte layer; and printing the anode on thepolymer electrolyte layer and placing the second metal current collectoron the anode; or printing the anode onto the second metal currentcollector and placing the printed anode on the second metal currentcollector in contact with the electrolyte layer.
 21. The lithium ink ofclaim 1, wherein the lithium ink has a viscosity of 1 to 30 Pa-sec at25° C.
 22. The lithium ink of claim 1, wherein the lithium ink has aviscosity of at least 10 Pa-sec at 20° C.
 23. The lithium ink of claim1, wherein the lithium ink comprises 10 to 30 percent lithium salt on adry weight basis.
 24. The lithium ink of claim 1, wherein the inkcomprises an electrically conductive material other than lithium metalpowder.
 25. The lithium ink of claim 24, wherein the electricallyconductive material comprises carbon.
 26. The lithium ink of claim 1,wherein the polymer binder comprises a polymer selected from the groupconsisting of: polyvinylidene fluoride; polyethylene oxide;polyethylene; polypropylene; polytetrafluoroethylene; polyacrylates;mixtures thereof and copolymers thereof.
 27. The lithium ink of claim 1,wherein the ink has a viscosity of 10 to 100 Pa-sec at 20° C.
 28. Thelithium ink of claim 1, wherein the lithium ink comprises: 20 to 50percent lithium metal powder; 10 to 25 percent of a polymer binder; 15to 40 percent of a conductive material; wherein the percentages arecalculated on a dry weight basis.
 29. The lithium ink of claim 28,wherein the ink has a viscosity of 0.5 to 50 Pa-sec at 25° C.
 30. Thelithium ink of claim 1, wherein the lithium ink comprises 5 to 25percent of a lithium salt on a dry weight basis.
 31. The lithium ink ofclaim 1, wherein the lithium ink comprises 10 to 15 percent of a lithiumsalt on a dry weight basis.